In the industry of Thin Film Transistor-Liquid Crystal Display (TFT-LCD), rotation of liquid crystal molecules is mainly controlled by the electric field generated between the pixel electrode and the common electrode so as to achieve the effect of displaying images to be displayed. Whether or not the potential of the pixel electrode can reach the required value mainly depends on the on-current Ion of the TFT.
Under the same process conditions, the width-to-length ratio W/L of the TFT has great impact on the performance of the TFT, wherein W is the channel width and refers to the extended distance from the start point to the end point of the channel, and L is the channel length and refers to the distance between the source and drain of the TFT. If other conditions remain the same, larger width-to-length ratio of the TFT means better performance, and the potential of the pixel electrode can reach the required value more easily. An increase in the width-to-length ratio of the TFT can be realized by increasing the channel width W or reducing the channel length L.
However, an increase in the channel width W will also result in an increase in the size of the TFT and a reduction of the aperture ratio. A reduction in the channel length L can both increase the width-to-length ratio of the TFT and reduce the size of the TFT, and can also increase the aperture ratio. Therefore, reducing the channel length L is the best way of increasing the width-to-length ratio of the TFT.